WYSTAN AUDEN reminded us that "doom is darker than any sea dingle," and who is there that doesn't entertain thoughts of disaster? Throughout Deliberate Regression Robert Harbison contemplates and seems certain the worst is yet to be. Oddly, Robert Adams remains sanguine after describing destruction, murder, greed, natural clamity and stupidity in The Lost Museum. He remains even-headed about what is left ovr, what can be enjoyed; the inevitable does not disturb his equanimity. Neither author is likely to send readers away from these books with faces wreathed in smiles.

When Harbison's first book, Eccentric Spaces, was published in 1977, everyone who read it must have been struck by its originality and bona fide charm. The feel, the shape, the nature of rooms, museums, gardens, buildings, streets, dwellings both real and imagined were described so freshly and personally that readers could not fail to respond to the "ecentric spaces" experienced by the author. Some of this same feeling for discovery is carried over into his new book when Harbison calls attention to lesser-known but fascinating 19th-century artists such as the decorators William Burges and Henry Wilson, or the Northern painters Philipp Otto Runge and Christen Kobke.

The rest of the artists, writers, philosophers dealt with seem to be there to illustrate Harbison's choleric conviction of a "disastrous history, how man is willed a stranger to himself and dissolved until not recognizably human any more." It was "nineteeth-century subjectivism [which] leads through personality to a depersonalized end." That end is the nightmare disintegration of man by the maniac tyrants, Hitler and Stalin. Harbison is as pessimistic as Spengler, perhaps more so. Since I personally share many of the author's negative feelings about man's appauling violence, I find it unpalatable that in his "readings" works of art are continually reduced to being mere symptoms of human mess. He comes down with sledgehammer blows on the eroticism of Boucher and Fragonard, he deplores the "cult of death" in David, he finds Kandinsky both unintelligible and insincere, he equates Nietzsche with Nazi ant-intellectalism. His argument becomes so exaggerated that one's only response to such humorless, Savanarola-like outpourings is to exclaim, "Balderdash!"

The downward path of Harbison's "regresive" types begins in the 18th century with Jean-Jacques Rousseau. Were people more rational, given to greater probity, more involved with reality before Rousseaau and before the beginnings of "Romantic individualism"? Was life better when everybody believed in God? Harbison does not make it clear what he believes in, or what he wants instead of what we've got. He argues his cases like an impassioned convert; to what end is not made clear. Nowhere does he convince that science and the arts -- including the avant-garde of the 20th century -- are other than the best signs of man's need to understand and live in the world decently and rationally. As for the official art of Hitler and Stalin, which for Harbison is the final straw, it remains what it was at the start -- profoundly vulgar junk.

It is a measure of Harbison's lack of control that his prose, lacking the elegant clarity of his first book, is overblown and faintly sour.

It is impossible not to be pleased with Robert Adams' good sense in The Lost Museum, about the perennial and continuous destruction of art. The old adage that life is short and art is long becomes turned about. There seems to be nothing that does not regularly and systematically get demolished; the most beautiful cities like Angkor Wat, chains of temples as in the Yucatan and Guatemala, whole civiliations as in the Middle East. Adams, however, is more interested in later periods of destruction and particularly where man's folly, greed or conceit is at work. He is fascinated by what existed and no longer does, but which can at least be glimpsed through documents, copies, fragments.

His findings are often delectable. Who would not like to see the Parthenon, which during Turkish occupation boasted a minaret, intact? Isn't it tantalizing to know Leonardo's celebrated Battle of Anghiari only through the copy by Lorenzo Zacchia? Imagine what Salisbury Catherdral was like before the suet-brained restorers got through "improving" it -- or St. Paul's before the great London fire. One finds oneself dreaming of Michelangelo's snowmen made for the Medici children or wishing to find Canova's lost, life-size sculpture of George Washington commissioned for the North Carolina State House in Raleigh, of which there is left only a tiny plaster model.

No doubt one of the largest accumulations of art occurred during the Middle Ages, and the majority of it was destroyed beyond retrieval. By the year 1415 there were about $15,000 Benedictine monasteries established across Europe -- pampered, decorated, adorned. Aside from being havens of contemplation, they served as schools, fortresses, embryonic cities, workshops, private clubs for the aristocracy. Architecturally magnificent, the monasteries contained vast collections of art in every form, libraries of exquisite books and manuscripts. Cluny alone with its huge network of little Clunys (perhaps 6,000) surpassed St. Peter's at Rome of sheer size, grandeur, wealth. Was it war, storms fires or the vicissitudes of religious rivalry and breakups that finally did the entire complex in? Today there are but a handful of these monasteries left. But supposing, wonders Adams, all 15,000 were still around? What would we do with them?

Ordinary people in the last few thousand years do not find this a vexing question. Everything gets used again -- stones from buildings, lead from stained-glass windows, gold is melted down and precious materials invariably stolen, sold, lost.

There are a few destructions which do manage to ruffle Adams' calm -- for instance such stupid razings as Frank Lloyd Wright's Larkin Building in Buffalo (up in 1904, down in 1949), H. H. Richardson's Marshall Field Building in Chicago demolished 45 years after its erection in 1885. We are reminded that Americans don't have very much to begin with, and that we should hang on to what we've got.

Cheerful to the end, Adams quotes an old phrase about Rome: "Quanta fuit ipsa ruina docet" -- How great she was even her ruins bear witness!